Trunking and supervisory system.



Patented Jan. 14, 1919.

4 SHEETS-SHEET l.

TTO/VEYS,

T. G. MARTIN.

TRUNKING AND SUPERVISORY SYSTEM. APrLlcArloN FILED usc. lo. 1910. nsmswsn luLY a. 191s.

WWA/55555 T. G. MARTIN.

TRUNKING AND SUPERVISORY SYSTEM.

APPLICATION FILED Dc.Io, I9Io. IIENEwEo IuLY a, Isls.

Patented Jan. 14,'1919.

4 SHEETS--SHEE 2.

Patented Jan. 14,1919.

4 SHEETS-SHEET 3.

mowza. 'n

T. G. MARTIN.

THUNKING AND SUPERVISORY SYSTEM. APPLICATION FILED Dec. Io. I9Io.y IIENIzwEn IuLY 8.1918.

T. G. MARTIN.

TRUNKING AND SUPERVISORY SYSTEM.

APPLICATION FILED nic. Io. I9Io. IIENEwED JULY 8.1918

1,291,586. Patented Ian.14,1919.

4 SHEETS-SHEET 4.

IIHIIIIIIIIIIIII WTA/55555 d @kmh/V UNITED sTATEs PATENT oEEIoE TALBOT G'. MARTIN, 0F CHICAGO, ILLINOIS, ASSIGNORTO AUTOMATIC ELECTRIC COMPANY, 0F CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TR'UN'KING AND SUPERVISORY SYSTEM.

'Application led December 10, 1910, Serial No. 596,711.

1 '0 all whom t may concern:

Beit known that I, TALBOT G. MARTiN,

and resident of Chicago, Cook county, Illinois, have invented `a certain new and useful Improvement in Trunkin and Supervisory Systems, of which the Io specification.

My invention relates to telephone systems of that particular character in which automatic switches are employed, such as selectors and connectors, and in whichsome of said switches are also capable of repeating impulses to other switches. Systems of this kind are sometimes two-wire and sometimes three-wire; and by this I mean that' in some cases the switches are operated by controlling the two sides of the calling line in series, mwhich case the system is known as a two-wire system, while in others the switches are controlled by grounding the line at the calling substation, in which case the system is known as a three-wire system. My invention relates to systems including both modes of operation.

The principal object of my invention is to provide a combined selector and repeater for connecting a two-wire system with a three-wire system, and for controlling the apparatus of the three-wire system to eX- tend connection to the called subscribers line, the said combined selector and reproved larrangement peater being controlled over the two sides of the calling line in series, whereby the said selector and repeater serves as the medium of connection and control between eX- change apparatus of one type and some of another type.

It is also an object to provide an imfor supervising a connection by reversing the current in the said circuit of a manual switchboard when the called subscriber answers.

Another object is to provide a combined selector and repeater that is controlled over the two sides of the calling line in series, and that will automatically ground one side of the line or talkin circuit to cause an automatic signaling o the called subscriber.

A further object is to provide a combined selector and repeater which will, when the called subscriber answers, reverse the current in, the direction of the calling subscriber for any useful purpose.

Specification of Letters Patent.

llowing is a Patented Jan. 14, 1919.

Renewed July s, 191s. serial No. 243,946.

It is also an object to provide certain novel features and combinations tending to increase the general efficiency of atelephone exchange system of this particular character.

To the foregoing and other useful ends my invention consists in matters hereinafter set forth and claimed.

In the accompanying drawings Figures l, 2' and 3 taken together represent a complete circuit connection between a calling substation A (Fig. l) and a called substation A (Fig. 3) of two different automatic eX- ychanges, in a system embodying the principles of' my invention. Fig. 4 represents diagrammatically an automatic connector switch of said system. Fig. 5 is a diagrammatic representation of the essential features of the so-called master switch D (Fig. l) of said system.

In Fig. 1 there is shown a line switch C which is individual to the line of substation A. A group of these line switchesis controlled by a common mechanism or master switch D. All of the line switches which are controlled by the master switch D have common access to a number of trunk lines leading to selector switches E. These selector switches have access to a number of trunk lines, some of which lead to operators jacks J. The automatic switches shown in Fig. l are of the so-called two-wire typethat is, the kind which are controlled from the calling substation over the two sides of the line in series. At O (Figs. 1 and 2) is represented an operators cord circuit. At F (Fig. 2) is shown a combined selector and repeater. In Fig. 3 there is shown a selector switch H, connector I, line switch C and substation A. The switches H and I (Fig. 3) are of the so-called three-wire type-that is, the type which is controlled from the callin station by impulses over the two sides 0% the line separately. The connector switch I', Fig. 4, is of the twowire type.

lIn the various drawings a number of ringin machines L and L are represented and a so a number of busy signaling machines M, M and M2, each comprising a current interrupter and induction coil, as shown, for supplying the necessary curr nt. For operating the switches and for talking purposes several batteries B are shown having one terminal grounded at G. There need be but one battery, however, or preferably one battery'in each exchange.

The two-wire substation A, Fig. 1, comprises the usual receiver 2, switch hook 3, transmitter 4, ringer 6 and condenser 7. Since it is an automatic substation it is also provided with the impulse springs 8 and 9 and an impulse Wheel 10 which carries upon its periphery a number of impulse teeth 11 and is secured to a shaft 13 to which there is also attached a dial (not shown) provided with finger holes. rlhe teeth 11 on the impulse wheel 10 are so arranged that as they are rotated forward to call any digit the springs 8 and 9 are not affected; but as the impulse wheel returns to normal position the springs 8 and 9 are separated by the teeth 11 a number of times corresponding to the digit called. The line switch C, Fig. 1, which is individual to the line of substation A, and the master switch D are modified forms of the general types of line and master switches disclosed in the British Patent No. 26,301 of 1906, and in the American Telephone Journal, of New York, N.. Y., of June 6, 1908. As herein represented, the

line switch C comprises, among other details, a plunger 14 (Fig. 5) attached to the end of a so-called plunger arm 15 which is lcontrolled by the magnet 16. The magnet 16 also controls the relay armatures 17 and 18, and is composed of four windings, namely, a pull-in winding 19, a holding or cut-off winding 20, line winding 21 and auX- iliary winding 22. The core of the magnetl is provided near the center of its length with a lateral projection 23, by means of which the ma net is attached t0 the bracket 24, upon w ich the armatures 17 and 18 are piv- `oted. With this method of mounting the magnet the magnetic circuit of the windings 19 and 20 is maintained separate from that of the windings 22 and 21, so that the armatureson one end of the magnet are not aected by the energization of the windings upon the other end.l Of the two windings upon the upper end of the magnet only the winding 19 is strong'enough to attract the plunger arm 15 from its normal position. Although the winding 20 is not strong enough to operate the plunger arm, it will hold it in its operated position after it has once been drawn down by the winding 19. When the plunger arm is attracted by the magnet 16, the plunger of the switch is forced into the bank of contact springs, forcing the springs 25, 27, 29 and 31 into engagement with the sprin s 26, 28, 30 and 32, respectively. Althoug only one set of springs (25-32) is shown, each line switch C is provided with a number of such groups of springs, each. group forming the terminal of a trunk line leading to a Selector E. Each trunk line is connected in multiple to the corresponding springs of all the line switches of the group which is controlled by the master switch D. The plungers of the line switches of this group normally engage the plunger shaft 33 (Fig. 5), and through the medium of the master switch D are normally maintained opposite the terminal of tory motion about the shaft 36, so as to move the idle plungers back and forth in front of their trunk terminals. To the shaft 36 there is secured a locking plate 38 provided on its outer edge with a number of openings 39 which are adaptedgto be engaged by the pin 40 upon the end of the armature 41 of the relay 42. The openings in the plate'38 are so spaced that the pin 40 can engage one of them only when the plungers that are 1n locking engagement with the plunger shaft are directly in front of the corresponding trunk terminal. The master switch is also provided with a bank of contacts comprising a common segment 43 and one individual segment a for each trunk to which the line switches have access. The wiper 44 always keeps the common segment in electrical connection with the individual segment corresponding to the trunk line before which the idle plungers are being held by the master switch.

rllhe selector E is of the general type disclosed in United States Letters Patent No. 815,321, granted March 13, 1906,'t0 Keith, Erickson and Erickson, being modified,how ever, in order to operate in a two=wire system. Among itsessential details, the selector E comprises the usual line and private wipers 45, 47 and 46 carriedupon a shaft (not shown) which has a vertical motion controlled by the vertical magnet 48 and a rotary motion controlled by the rotary magnet 49. The side switch comprising the wipers 50, 51, 52 and 53 is controlled by the private magnet 54 in the usual manner. The release magnet 55 is connected with the battery only when theswitch shaft is raised 57, 58 and 59 denergize slowly after their energizing circuits have been broken.' T his slow action may' lie-accomplished by securing a ring of copper or other conducting material around one end of the core. The selector is also provided with a bank of contacts which are adapted to be engaged by the wipers 45, 46 and 47.

The operators cord O (Figs. 1 and 2) is similar to the usual type of cord circuit used in manual switchboard practice, the supervisory circuits being modified, however, to operate in the system disclosed herein. The cord is provided with an automatic calling device similar to that at t'he substation A and represented diagrammatically by a pair of impulse springs 60 andl 61. The supervisory relay 63 is an ordinary polarized relay-that is, it will attract its armature in a direction to close contact between the springs '64 and 65I only when the current flows through it in a particular direction.

The selector-repeater F combines the functions of 'a selector and a repeater-that is, it operates in response to the impulses for one digit to select a trunk line, and in response to the impulses for the remaining digits to repeat impulses over` this trunk line to succeeding switches. The essential features of the selector F are very similar to those of the selector E (Fig. 1), with the addition of a number of relays which are required for the additional function of repeating impulses. Like the selector E, the selector F is adapted to be controlled over the two sides of the line in series, but repeats impulses over the two sides of the trunk line separately. Therefore, 4the switch F is in the nature of a so-called two-wire selector and two-wire to three-wire repeater. It comprises the usual line and private wipers 66, 67 and 68, vertical magnet 69, rotary magnet 70, private magnet 71 and a side switch comprising the wipers 72, 73, 74, 75 and 76. The switch F is also provided with an auxiliary magnet 77 which operates the ratchet wheel 78. This ratchet wheel 78 so controls a pair of springs 79 that-said springs are permitted to come into contact every time the wheel is rotated our steps by the magnet 77. The talking circuit through the selector-repeater contains the condensers 80 and 81.

The selector H (Fig. 3) is similar to the selector described in the said selector Patent No. 815,321, and, like it, is adapted to be operated over the two sides of the line separately. The connector I Vis of the general type of connector switch disclosed-in United States Letters Patent No. 815,176, granted March 13. 1906, to Keith, Erickson and Erickson, the circuits being modified somewhat in order to operate in a common battery system. The line switch C is 0f the' general type of line switch disclosed in the Americain Telephone Journal, of New York, N. Y.. of June 6, 1908, and comprises the usual trip magnet 82, release magnet 83 and cut-ofi1 relay 84. The line switch C', together with a number of other similar switches, is "ontrolled by a master switch similar to the master switch D (Fig. 1). The connector I (Fig. 4) is similar to the Connector I, being modified, however, to operate in a two-wire system.

Having given a general description of the apparatus, I will now explain in detail the operation by which the subscriber at substation A of the two-wire exchange may obtain connection with the substation A of the three-wire exchange.v The switches C and E must rst be operated to signal the operator at the cord O, after which connection is com-l pleted by said operator through the switches F, H and I to the required substation. The switch C is operated immediately upon. the removal of the receiver at the substation A in the following manner: The removal of said receiver permits the switch hook to rise, thereby permitting the spring 85 to engage the spring 85, whereby -a circuit is completed through the line winding 21 of the line switch C. This circuit extends from ground G through the springs 86 and 87, line conductor 88, springs 85 and 85, impulse springs 9 and 8, receiver 2, transmitter 4, line 89, springs 9() and 91 and line winding 21 to the battery lead 92, thence through the battery B to ground G. The winding 21, upon energizing, attracts the armature 18, which forces the spring 93 into engagement with the spring 86, thereby completing a circuit from ground G through the springs 86 and 93, windings 19 and 22, contact point 94 and armature 41 to the battery lead 92. The winding 19, upon energizing, attracts the plunger arm 15 and cut-ofi' armature 17. The attraction of the plunger arm l5 causes the line connection to be eX- tended through the springs 25 and 26 and 27 and 28 to the' selector E, whereupon the line relay 62 becomes energized over a circuit extending from ground G2 through the v51 and through the upper winding or' the relay 62 to the battery lead. The relay 62, upon energizing, operates to complete a circuit extending from ground G3 through the springs 95 and 96 and relay 57 to the battery lead 92. The relay 57, upon energizing, operates to connect the relay 59 with the impulse spring 97 of the relay 62, and to complete a holding circuit for the winding 20 of the line switch C. This circuit extends Jfrom ground G4 through thc sp1-ings 98 and 98, 30 and 29 and winding 20 to the battery lead 92. The energization of the winding 20 serves to hold the plunger arm 15 and cut-ofi' armature 19 in their operated positions after the circuit of the pull-in winding 19 has been broken by the falling back of the armature 18. The circuit of the line winding 21 by which the armature 18 was attracted is broken as soon as the cut-oli armature 17 is pulled up, but the armature 18 is held in its operated position for an instant thereafter, due to the `fact that the auxiliary winding 22 is short-circuited at the springs 99 and 100 by the plunger arm, and therefore caused to denergize slowly. This insures that -the circuit of the winding 20 shall be closed before the plunger arm has time to fall back upon the denergization of the winding" 19. The energization of the relay 57 of the selector E also extends a guarding potential from ground G4 to and through the line switch bank springs 30 and 29, and over the private normal conductor 101 to the connector private bank contacts of the calling line, to prevent said line from being interfered with while it is vin use.

The engagement of the springs 31 and 32 upon the operation of the line switch C completes a circuit from ground G5 through said springs 31 and 32, contact point 102 (which corresponds to the trunk line leading to the selector E),wiper 44 and relay 103 to the battery lead 92. The relay 103, upon energizing, completes a circuit through the relay 42. The relay 42, upon energ1zing, operates to withdraw the pin 40 from the locking plate 38, and to close a circuit through the motor magnet 34. This circuit extends from ground Gr8 through the magnet 34, interrupter springs 330, contact point 104 and armature 41 to the battery lead. The magnet 34 thereupon 'begins to operate in a manner similar to Vthat of a buzzer to advance the idle plungers away from the trunk seized by the switch C. After the plungers have been advanced a short distance the wiper 44 passes off the contact 102, thereby breaking the circuit of the relay 103, which denergizes and in turn breaks the energizing circuit of the relay 42. The armature 4l does not fall back immediately upon the denergization of the relay 42 because the opening in the plate 38 which was engaged by the pin 40 has moved out of. register therewith. Therefore, the armature 41 remains in contact with the contact point 104, and the magnet 34 continues to advance the plungers until the next opening in the plate passes under the pin 40. If the next trunk is idle, the pin 40 drops into this opening and allows the circuit of the magnet 34`to be broken. If this next trunk is busy, how"- ever, the wiper 44 will -in'd a guarding ground potential upon a corresponding bank contact, causing the relays 103 and 42 to remain energized while the opening in the plate 38 is passing beneath the pin r40, and the plungers will be carried past the busy trunk line to an idle one. While the master switch is operating, the armature 41 is disengaged from the contact point 94,

thereby disconnecting the pull-in winding 19 of the line switch C and the battery lead 92, thus making it impossible for any line switch to be operated while its plunger is being moved from yone trunk to another.

1t will be assumed that the trunks leadving to thejacks J are connected with the selector line relay 62 is broken momentarily.y

Since the relay 57 is slow acting it does not have time to denergizeduring the momen-v tary interruption 0f this circuit by the operations of the relay 62 in response to these impulses, and, therefore, each time the relay 62 denergizes, a circuit is closed from ground Gr3 through the springs 95 and 97, 105 and 106, relay 59, vertical magnet 48 and side switch wiper 50 to the battery lead 92. Since the digit called is 2, the vertical magnet receives two impulses over this circuit, operating to raise the shaft wipers two steps to a position opposite the second row of bank contacts. The relay 59, which is included in the energizing circuit ofthe vertical magnet, is energized by the first impulse, and, being a slow-acting relay, does not denergize until after the last impulse has been delivered. In its energized position the relay 59 completes a circuit from ground Gr8 through the springs 107 and -108 and private magnet 54 to the battery lead 92. When this circuit is broken by the deenergization of the relay 59, after the last impulse is delivered to the vertical magnet, the private magnet denergizes and permits the side switch to pass from rst to second position.

The movement of the side switch wiper 50 from lirst to secondv position disconnects the battery from the vertical magnet 48 and completes a circuit through the rotaryrmagnet 49. This circuit extends from ground G2 through the interrupter springs 109, magnet v49, relay 58 and side switch wiper 50 to the battery lead 92. Since this circuit includes the interrupter springs 109, the rotary magnet 49 will continue to operate in a manner similar to that of a buzzer to rotate the wipers step by step as long as the side switch remains in second position. the rotary magnet energizes, its armature presses down the armature of the private magnet 54, and if the first trunk line upon which the wipers are rotated is not busy, the armature of the private magnet falls back as soon as the rotary magnet denergizes the first time, and permits the side switch to pass to third position. 1f the first trunk is tion, the seized trunk is protected from inter-V energizes and permits the side switch to pass to second position. In Vsecond position the side switch wiper 76 completes the circuit of the rotary magnet 70, which circuit extends from ground .G18 through' the interrupter springs 154, rotary magnet 70 and' ference by a guarding potential extending from ound G14 through ,the side switch wiper 3 and private wiper 68 to the private bank contacts in all of the selectors which have access to the said trunk.

When the operators calling device is operated for the second digit- 2, the line relays 134 and 144 operate in the same manner as explained for the rst digit, but with a different result.` Each time the relay 134 deentrgizes, a circuit is closed from ground G11 through thesprings 156 and 157, 158 and 159, side switch wiperf74, relay 152, resistanc'e 358 and side switch wiper 76 to ,the battery lead 145. The relay 152, upon energizing, operates to close the circuit of the private magnet 71, which operates to disconnect the condensers 8O and 81 from the trunk conductors 169 and 170. The energlzation of the relay 152 also completes a4 circuit from ground G15 through the springs 161, relays 162 and 163 and side switch wiper 7 2 to the battery lead. The relays 162 and163 are both energized over this circuit and remain operated until the relay 152 deenergizesafter the last impulse has been delivered for the digit. Each time the springs l46 and 149 come into engagement, upon the denergization of the relay 144, the trunk conductor 169 is grounded over a circuit extending from lground G12 through the springs 146 and 149, 150 and 151 and wiper 75 to the conductor 326, springs 171 and 172 and wiper 66 to the conductor 169. From the conductor 169 these impulses pass through the side switch wiper 173 of the selector H (Fig. 3) and the vertical line relay 174 to the battery lead 145. Each time the relay 174 energizes, a circuit is closed from ground G17 through the springs 175 and 176, 178 and 179 and vertical magnet 180 to the battery lead. Since the ldigit called is 2, the vertical magnet receives two impulses and operates .to raise the wipers 181, 182 and 183 two steps. The line relays of the selector F remain in their energized position after the last impulse for the'digit is delivered by the operators callcuits of the private magnet 71 and relays 162v and 163. The private magnet 71 and relay l63 fall back immediately, -while the slow actin relay 162 remains in 'its energized position for a short time. At the instant the relay 163 falls back, a circuit is closed from ground G6 through the springs 187, 186, 185 and 184 of the relay 162, springs 188 of the relay 163 and magnet 77 to the battery lead 145. The magnet 77, upon energizing, opcrates to rotate the wheel 78 one step. Another result of the denergizing of the relay 163 is the grounding of the trunk conductor 170 over a circuit extending from ground G1 through the springs 187 and 186, springs 189 and shaft wiper 67 to said conductor 170. From the conductor 170 this impulse passes through the side switch wiper 190 and line relay 191 of the selector H. to the battery lead.' The relay 191, upon energizspo ing, operates to close a circuit from `ground v G17 through the springs 175 and 177 and private magnet 192 to battery. When the relay 162 of the switch F denergizes, the circuits which were closed by the rela -163 are broken. The relay 191 of the vse ector H thereupon denergizes and breaks the circuit of the private magnet 192, which in turn denergizes and permits the side switch to pass to second position, whereby a circuit is closed through v`the rotary magnet 193. This circuit extends from ground G through the side switch Wiper 194, interrupter springs 195 and magnet 193 to battery. The rotary magnet 193 then operates in the same manner as explained forthe rotary magnet of the selector E to rotate the `wipers onto the contacts of an idle trunk,

after which the side switch passes to third position in the usual manner. In case the wipers have to rotate over busy trunks, the energizing circuit for the private magnet 192, which causes the side switch to be locked in second position, extends from the guarded private bank contacts of the busy trunks through the wiper 183, relay 196, side switch wiper 197 and private magnet 192 to battery. The relay 196 is not energized over this circuit due to the comparatively high resistance of the magnet192. When the side switch passes to third position the connection is extended through the wipers 181 and 182 to the connector I, and said connector is guarded against being seized by another selector by a ground potential which extends from ground G19 through the side switch wiper 197, relay 196 and wiper 183 to the selector private bank' con` tacts of the trunk leading to the connector The operators calling device is now operated for the third digit 2. The selector-'redie 'iacutea busy, guarding ground potential upon the private bank contact, and completes .an energizing circuit through the side switch wiper 53 vand private magnet 54 to the battery lead 92. The private magnet 54 thereupon energizes and locks the side switch in second position, andthe rotary magnet-continues to advance the Wipers step by step until the private wiper 46 engages the nongrounded Contact of an' idle trunk, whereupon thel rivate magnet 54 denergizes and permits the side switch to pass to third position. rl`he movement of the side switch wipers 51 and 52 from the second to connects the line relay 62 from the line, and extends a connection. through the wipers 45 yand 47 and the condensers 11() and 111l to and also completes an energizing the relay 112. rlhis circuit extends from ground G7 through the lower winding of said relay, wipers 47 and 52, thence to and through substation A and baclr over the other side of the line, and through the wipers 51 and 45 and upper winding of the relay 112 to the battery lead. The relay 112, upon energizing, extends a guarding potential :from ground G8 through the springs 113 and 114'to the selector private banl contacts 115 or the seized trunk, and also coinpletes a circuit through the relay 116 at the jack d. This circuit extends "from the battery -lead'92 through the lower winding of the relay 117, springs 118, 119, relay' 116, springs 120 and 121, springs 122 and 123 and upper winding of the relay 117 to ground G". The relay 116, upon energizing, completes the circuit of the lamp 124. The relay 117, upon energizing, provides a second holding ground for the selector release relay 57. After the side switch of the selectorv E has left second position, the relay 62 denergizes; but the release relay 57 is maintained energized by a circuit extending from ground the jack d, circuit for G8 through the springs 113 and 114 of the` private bank contact 115, private relay 112,

wiper 46, side switch wiper 53, springs 125 and 126 and relay 57 to the battery lead. Although the relay 58 is slow acting, it is not as slow as the relay 57, so that the relay 58 denergizes soon enough after the last energization of the rotary magnet to perinit the closure of the circuit through the relay 57 before it has time to denergze alter its circuit is broken by the relay 62. The operator, upon seeing the signal of the lamp 124, inserts the plug P into the jack d, whereupon the circuit is completed from ground G31 through the relay 1.27 ol the cord U, conductor 128, sleeve conductor of the plug P vand jack d' and relay 129 to the battery lead 92. The relay 129, upon energizing, operates to .disconnect from the line, whereupon said relay denergizes and brealrs the circuit of the lamp 124.

however, the private wiper 46 nds a the cord tains the `second' relay'? or `the selector E, so that said relay the third position dis- G12, through the springs 4switch wiper 75,

the relay 116k .The insertion or the plug l? into the jack also completes a circuit from ground G1 at .l

130, ring conductors of the plug 'P and jack J and the lower winding of the relay 117 to the battery lead 92; andat the saine time a second circuit is completed extending from ground G9 through the upper winding of the relay 117, springs 122' and 123, tip conductors of the jack d and plug?, conductors 131 and 132 and relay 183 to the battery lead 91,2. The relay 117 remainsxenergized and mainholding v ground for the 57 cannot now denergiae until both relays 112 and 117 are denergiaed. The energizetion of the relay 133 at' the cord has no particular edect at this time.

through the relay 32'?, conductor After ascertaining the number bi the de I' sired substation, the operator inserts the plug P into the jackd, operates the lacy K to line, and then operates the callin device for the number oi'.2 the called su station, which, in this case, is assumed to be 2229. l/Vhen the plug is inserted intov the jaclrea circuit is completed from ground through the relay 134, springs 185 and 186, conductor 13'?, sleeve conductors of d" and plug 1P, device springs 66 and`61, and 146, tip o1 the plusr lm springs 142 and 148 and tery lead 145. The relays 184 and 144 are both energized over this circuit, the relay 144 operating to close a circuit roin ground 146 and 14'( and battery lead 145. |lha enerand jack d,

relay 148 to the bridge the calling device across the the jaclr `springs 138 and 139, calling lrey springs 141 raelay 144 to the batgization of the relay 134 has no edect at this time. llhen the operators calling device is operated tor the iirst digit 2, the. springs 60 and 61 are separated twice momentarily, thereby allowing the. relays 134 and 144 to be deenergized twice.A The operation of the relay 134 is without eect. atthis time. Since the relay 148 is slow acting it does not denergize" during the Mll momentaryinterruption of its circuit by the relay 144;-there1ore, each time said relay 144 denergizes,

a circuit is closed trom' ground G12 through the springs 146 and '149, springs 150 and 1510i the relay 148, side relay 152, vertical magnet 69 and side switch wiper 7 6 to .the battery lead. The vertical magnet is y energized twice over this circuit, operating to raise the wipers 66, 67 and 68 two steps. rlhe private magnet relay 152 operates in the same manner as explained for the relay 59 in the se 'lector E to close the circuit 'of the private magnet 71 while theiinpulses are being` de' livered to the vertical magnet 69. iter the last of these impulses is delivered, the relay 152 denergizes and breaks the-circuit l of the private magnet 'l' 1, which in turn depeater F operates in response to the impulses for the third digit in the same manner as for the previous digit to repeat two ground impulses to -the trunk conductor 169, followed by one impulse over the conductor- 170, and to energize the magnet 77 once more to rotate the wheel 78 a second step. Since the connection is now extended to the connector I, the impulses for the third digit which are repeated to the conductor 169 pass through the side switch wiper 173 and shaft wiper 181 of the selector H, and through the relay 198 and upper windin of the relay 199 of the connector I to the attery lead 145. The energization of the relay 199 at this time is without function. The relay 198, however, upon energizing, completes a circuit from ground G2vthrough the springs 200 and 201, 202 and 203, side switch wiper 204 and vertical magnet 205 to the battery lead 145. The Vertical magnet receives two impulses over this circuit and raises the shaft and |wipers two steps. The impulse for the third digit, which is repeated over the conductor 170, passes through the wipers 190 and 182'of the selector H, through the rotary line relay 206 of the connector I,lower winding of the relay 199 and springs 207 'and 208 to the battery lead. The relay 206,

upon energizing and denergizing, sends an impulse from ground G20 through the springs 200 and 209, private magnet 210 and springs 207 and 208 to battery. The private magnet 210, upon energizing and denergizing, permits the side switch to pass from irst to second position, whereby the connec tion of the impulse spring 201 is'transferred from the vertical magnet v205 to the rotary magnet 211 through the medium of the wiper 204.

The selector-repeater F operates in response to the impulses produced by the operators calling device for the fourth digit in the same manner as for the previous digit to repeat the impulses to the connector. Since the last digit is 0, ten impulses .are transmitted over the conductor 169, and the 'connector line relay 198 is energized ten times. Since the side switch is in second position, the energization of the relay 198 in response to these impulses transmits ten im? pulses through the rotary magnet 211, which operates to rotate the shaft .wipers ten steps onto the contacts of the line 2220. The rotary line relay 206 is now Yenergized by the impulse over the conductor 170 and sends a second impulse through the private magnet 210, which causes the side switch to pass to third position. When the side swltch wipers 212 and 213 reach the third position, the connection is extended through the shaft wipers 214 and 215 to the called line. The

engagement of the side switch .wiper 216 with its third-position contact point extends a guarding potential from ground G2l to the energizes,

private wiper 217, and thence to the private bank contact of the called line in the bank of each connector which has access to said line. This guarding potential protects the called line from being seized by any other connector. The side switch wiper'2l6, in third position, also completes a circuit from ground G21 through the wipers 216 and 217 and the cut-ofi:l relay 84 of the line switch C to battery. The relay 84, upon energizing, operates to disconnect the switch C from the called line, and completes the connection from the wiper 215 to the line 218. At the switch F the magnet 77 is again energized at the time the last impulse is delivered to the conductor 170, whereby the wheel 78 is rotated a third step. This third step of the wheel 78 permits the springs 79 to come into engagement. Thus, as soon as the slow acting relay 162 denergizes, a circuit is completed from ground G22 through the interrupter 219, springs 79, 220 and-221, 'springs 222 and relay 223 to battery. The relay 223 is energized intermittently over this circuit, operating to transmit a series of impulses from ground G23 through the springs 224 and 172 to the conductor 169. These imulses over the conductor 169 cause the reays 198 and 199 of the connector to be energized, as explained in connection with the last two digits. The energization of lthe relays 198 and 199 at this time Vcompletes a circuit from ground'G20 through the springs 200 and 201, 202 and 203, side switch wiper 204, ringer relay 225 and'springs 226 and 227 to battery.` Each time the relay 225 the talking circuit is opened at the springs 228 and 229 and a signalin circuit is completed from one termina ofthe generator L through the springs 239 and 238, side switch wiper 212,y wiper 214, line 237, condenser 233, ringer 234, springs 235 and 236, line 218, springs 232 and 231, wipers 215 and 213 and springs 229 and 230 to the other terminal of the gen` erator L. Since the circuit of the relay 223 of the selector F includes the interrupter 219, the ringer relay 225 of the connector will be energized only intermittently so as not to ring the called subscriber continuously.

After the calling device at the cord has been operated for the last digit of the called number, the key K is restored to normal position, whereby the calling device is disconnected from the line and the relay 63 substituted therefor in circuit with the relays 144 and 134 of the switch F. The current flows through the relay 63 in such a direction at this time as to cause the armature to be attracted in the proper directionfor closing the springs 64 and 65. whereby the lamp 240 is lighted.

When the called subscriber removes his rcceiver from the switch hook. or :is soon thereafter as the relay 225 denergizes, if

relay 246 and springs 248 and 227 to the battery lead 145. The closure of this circuit furnishes talking current to the called.

substation and causes the relay 246 to energize. The relay 246, upon energizing, shifts the connection of the lower winding of the relay 199 from battery to ground, whereby an ener izing circuit is completed from ground 21 through the side switchvwiper 216, springs 249 and 207, lower Winding of "the relay 199, relay 206, wipers 182 and 190,

conductor 170, wiper 67, private magnet springs 250, relays 251 and 252, springs 253, private magnet springs 254, springs 171 and 172, wiper 66, thence to and through the relayv198 and upper winding of the relay 199 to battery. The relay 199 is not energized over this circuit because current flows through its two windings in opposite directions. The relays 198 and 206 are energized, but have no function. At the selector F the energization of the relays 251 and 252 transposes the connections between the line relays 134 and 144 and the two sides of the 'trunk leading to said selector. This transpositionpf the connections of the relays 134-and 144 results in the reversal of the current in the relay 63 of the cord O. The relay 63 thereupon attracts its armature in the opposite direction and breaks the circuit of the lamp 240, which signifies to the operator that the called subscriber has answered.

The energization of the relay l251 of the selector 'F also serves to close a circuit from ground Gr24 through the springs 255 and 256 relay 257 and side switch wiper 72 to the battery lead'145. lThe relay 257, upon energizing, breaks the circuit of the relay 223 so that the ringer relay of the connector I will not be operated againv after the called subscriber answers. When the relay 257 energizes it also forms a locking circuit for itself through its springs 258 and 259, so that it cannot denergize until the side switch is restored from third position, and

therefore the bells at the called station will` not be rung again when the called subscriber hangs -up his receiver.

After a conversation is completed, the hanging up of the'receiversr at the calling and called substations gives the operator the usual disconnect signals as follows: The hanging up of the receiver at the calling substation breaks the energizing circuit of the relay 112 (Fig. 1), which, upon denergizing, breaks the circuit through the upper winding of the relay 117 and relay 133 at 'cuit of the winding tends from the cord O. r1`he relay 133, upon denergizing, `closes the circuit of the lamp 260. The hanging up of the receiver at substation breaks the circuit of the connector back-bridge relay 246, which denergizes and in turn destroys the energizing circuit of the relays 251 'and 252 of the selector F. These'relays, upon denergizing,

removed from their respective jacks, whereupon the automatic switches employed in the connection are automatically released. The removal of the plug P from the jack J breaks the circuit of the relay 117, which deenergizes and, since the relay 112 ,is already denergized, breaks the circuit ofthe release relay 57 of the selector E. The relay 57, upon dene'rgizing,

20 of the line switch C and closes7 the circuit of the release magnet 55. This circuit extends from ground Gr3 through the springs 95. and 97, 105 and 261, magnet 55 and springs 58a and 57a to the battery lead 92. The winding 20 of the switch C, upon denergizing, permlts' the plunger of said switch to return to normal position. upon energizing, immediately causes the shaft and side switch of the selector to be restored to normal position. When the shaft 'reaches its lowest position, the springs 57 the called destroys the holding cir- The magnet 55 of the selector E,

from the jack J', the circuit of the line relays 134 and 144 of the selector-repeater is broken. The relay 134, upon denerglzing, operates to close the-circuit of the relay 152, which in turn closes the circuits of the relays 162 and 163, which circuits have been previously traced. The relay 144, upon denergizing, breaks the c 1rcu 1t of the relay 148, which breaks the clrcuit of the relay 152. r1`he relay 152, upon de, energizing, in turn breaks the .circuit of the relays 162 and 163. The relay 163 falls back immediately landl grounds the conductor 4170 and energizes the magnet 77 again in a manner already explained. The magnet 77 operates to advance the wheel 78 another step, which causes the sprlngs 79 to be separated. Since the line' relay .134 is denergized, the denergization of the relay 163 also grounds the conductor 169 at the same time it grounds the conductor 170. This ound connection exground 16 through the springs 187, 186 and 185 of the relay 162, spring 262 of the relay 163, and springs 165 and 13o and 227 to the battery lead 145. The magnet 266, upon energizing, causes the shaft and side switch of the connector to be immediately restored to normal position, while the relay 196 closes the circuit of the release magnet 267 of the selector H. The

magnet 267 attracts its armature and holds it in readiness 'to release the selector when its circuit is broken by the deenergization of the relay 196, when the slow acting relay 162 of the selector-repeater F denergizes and allows 'the line relays of the connector I to be denergized. The deenergization ofthe relay 162 of the selectorrepeater F also serves to close the circuit of the release magnet 268 of said selectorrepeater. This circuitextends from ground Gr16 through the springs 187 and 269, 270 and 271, magnet 268 and oli-normal springs 272 and 273 to the battery lead. The ma net 268, upon energizing, causes the switi F to be restored to normal position, and all the apparatus employed in the connection is left in readiness for another call.

In the releasing operations just described Y it will be seen that the connector I is not released until both the `trunk conductors 169 and 170 are grounded by the denergization of the relay 163 when its circuit is broken by the relay 152. It will also be seen that .the trunk conductor 169 `is grounded alone as soon as vthe line relay .144 denergizes, and remains grounded until the relay 148 denergizes. This ounding of the conductor 169 would cause the bells of the called substation to be rung for an instant. This, however, would be of such short duration as not to be liable to be mistaken for a calling signal and, therefore, may not be considered objectionable. If desired, however this short ring preceding the release may be entirely eliminated if, instead of connecting the thirdposition contact point of the side switch wiper 75 to the conductor 326 direct,'said contact is connected with said conductor a pair of springs normally closed, but adapted to beopened by the wheel 78 when it reaches the position shown in the drawings. Thus, after the last digit has been called, the impulse spring 149 would b e disconnected from the trunk conductor 169, and would not be again connected therewith until after the connection had been released.

Let it now be assumed that at the time the and springs 226 and 227 to the battery lead 145. The magnet 266, upon energizing, restores ythe connector to normal position and thus prevents connection with .the busy line. Now, when the vertical relay 198 is energized by the impulses delivered by the relay 223 of the switch F, instead of closing the circuit of the ringer relay, it closes the circuit of the vertical magnet, because the side switch has been restored to normal position. As soon as the shaft is raised the first step the arm 277 permits the springs 278 to engage, whereby the busy signaling machine M is connected to one side of `the calling line through the side switch wiper 213 and the heavy talking conductor. The calling subscriber, therefore, hears the busy signal and hangs up his re- 4springs 275 and 2 6, release magnet 266 signal, whereupon the connection is released in the manner explained above.

It having been explained how the o erator at the cord O obtains supervision o a call to a three-wire exchange through a selectorrepeater F, it will now be explained how supervision is obtained when the call goes toa two-wire exchan e. In this case the connection with the ca led line is through a two-wire connector I (Fig. 4). The connection from the cord O to the connector I maybe direct from .a jack or through one or more selector switches similar to the selector switch E (Fig. 1). As soon as the connection is extended to the connector, the line relay 279 is energized in circuit with the operators calling device. The relay 279 o erates to close the circuit from groun GE through. the springs 280 and 281 and the relay 282 to battery. The relay 282 being slow acting remains energized during the momentary interruptions of its circuit by the relay 27 9, while it is operating in response to impulses. Consequently, each time the relay 27 9 denergizes in response to the impulses for the next digit, -a circuit is closed from ground G2 through the springs 280 and 283, 284 and 285, relay 286, vertical magnet 287 and side switch wiper 288 to battery.

The relay 286 is energized by the first impulse through it in series with the vertical magnet, but being slow acting remains line.

" and 300 and side switch wiper 288 to battery. The relay 298 is energized intermitenergized until after the last impulse is delivered. 1n its energized position the relay 286 closes a circuit from ground G27 through the springs 289 and 290 and private magnet 291 to battery. When the private magnet den'ergizes after the last impulse has been delivered to the vertical magnet, it allows the side switch to pass to second position, whereby the battery connection is shifted from thel vertical magnet 287 to the rotary magnet 292. Each time the line relay 27 9 denergizes in response to the impulses for the last digit of the called number, a circuit is closed from ground G26 to and through the relay 286, as traced for the previous digit, and thence through the springs '293 and 294,'rotary magnet 292 and side switch wiper 288 to battery. The relay 286 Operates in response to the impulses for this digit to again close the circuit of the private magnet 291. If the called line is idle the private magnet denergizes after the last impulse is delivered to the rotary magnet, and the side switch passes to third position, completing the connection with the called The called line is immediately protected by a guarding potential which extends from ground G28 through the side switch wiper 295 and private wiper 296 tothe private bank contacts of the called line in the banks of all connectors which have access to said line. The movement of the side switch wiper 288 to third position complete's a circuit from ground G22 through the interrupter 297, relay 298, springs 299 tently over this circuit, and operates to open the connection between the calling and called lines and bridge the ringer generator L across the called line.

When the operator at the cord O restores the key K after completing the call, the relay 63 is energized in series with the two windings of the connector line relay 279, and closes the circuit of the'lamp 240;

The `irst time the ringer relay 298 deenergizes, after the called subscriber *removes his receiver, the called substationlis provided with talking battery current over a .circuit extending from ground G20 through the right-hand winding of the relay 301, private magnet springs 302, thence over the eavy conductors through the wiper 303 to the line of the called substation, thence back 'to the wiper 304;, over the heavy conductors the springs 306 and 307 into contact with their `alternate contacts, transposes the connections between the windings of the relay Y 279 and the trunk conductors 308 and 309,

thereby reversing the current in the relay 63 of the cord O. The relay 63 then attracts its naeiee armature in the opposite direction andextinguishes the lamp 240. When the called subscriber hangs up his receiver the relay 301 denergizes and restores the current in the relay 63 to its original direction, and the lamp 240 is again lighted. When the backbridge relay 301 energizes it also closes a circuit from'ground G26 through the springs 280 and 281, 310 and 311 and relay 312 to battery. The relay 312, upon energizlng, breaks the circuit of the relay 298 at tne springs 299 and 300, so as not to ring the called subscriber after he has answered. lThe relay 312 also closes a locking circuit 'for itself to prevent the ringer relay circuit from being closed again when the called subscriber hangs up his receiver. The locking circuit of the relay 312 extends from ground G2B through the springs 280 and 281, side switch wiper 313, springs 314 and 315, 316 and 317 and relay 312 to battery.

When the operator removes the calling plug from its jack after a conversation is completed, the connector line .relay 279 denergizes and breaks the circuit of the relay 282. Therelay 282, upon denergizing, completes a circuit' from ground G26 through the springs 280 and 283, 284 and 318, release magnet 319 and oii' normal springs 320 to battery. The magnetv 319, upon energizing, causes the shaft and side switch to be returned to normal position, and its own circuit is broken at the springs 320 when the shaft reaches its lowest position.

If the called line had been busy the private wiper 296 would have found the private bank contact grounded, and would have completed a circuit from said grounded contact through-the wiper 296, side switch energized after the relay 286 denergizes,

and locks the side switch in second position, thereby preventing the completion of connection with the called line.i This circuit p also prevents the relay 321 from denergizing- 1n case the guarding potential is removed from the private bank contacts of the called line before the connector is released. `As long as the relay 321 is energized, the busy signaling machine M is connected with the callin 324 and side swltch wiper 325, whereby the calling subscriber is notied of the busy condition of the called line.

From the foregoing it will be seen that I provide a system in'which efficient superviline through the springs sion is obtained for a semi-automatic con? nection by reversing the current in theL cord circuit of a manual switchboard. It

will also be seen that I provide 'a combined selector and repeater for use in calling from a two-wire system to a three-wire system.

In this case the three-wire system is of the kindV in which the switches are controlled.-

by alternating one orJ more impulses over one side of the calling line with a single impulse over the other side thereof. Also, the entire system is of the common battery type inwhich the exchange is divided into groups, and in which the selectors and connectors have vertical motion to select a predetermined group, and then rotary. motion to nd a unit in the selected group.

What I claim as my invention 1sv 1. In a telephone system, a plurality of subscribers lines', automatic trunking switches one for each of said lines, a

`for groundin plurality of trunks, an automatic switch for each trunk, an automatic trunk selector common to said lines rovided with means trol the switc at the other end thereof by alternating one or` more ground impulses over one `side of the trunk with a single impulse. over the other side thereof, and means for controlling said selector over two sides of a line circuit in series.

2. In a telephone system, va plurality of.

trunks, an automatic switch for each trunk, an automatic trunk selector provided with means for grounding any selected trunk to control the switch at the other end thereof by alternating'one or more ground impulses over one side of the trunk with a single impulsel overv the other side thereof, and means for controlling said selector over two sides of a line circuit in series, the said selector provided with mechanism for automatically causin an intermittent grounding of one side of e selected trunk, and means responsive to said intermittent grounding for 4 transmitting a signal.

3. In a telephone system, a plurality of *.trunks, an automatic switch for each trunk,

an automatic trunk selector provided with means for grounding any selected trunk to control the switch at the other end thereof by alternating one or-more ground impulses over one side of the trunk with a single impulse over the other side thereof, and

means for controlling said selector over two sides of a.- line circuit in series, said selector having means controlled by a calledv party forI reversing the current in the said line circuit.

4. In a telephone system', a plurality of trunks, an automatic switch for each trunk, an automatic trunk selector provided with means for grounding any selected trunk, to control the switch at theother end thereof by alternating one or more ground impulses over one side of the trunk with a single impulse over the other side thereof, and

4selected trunk to sign any se ected trunk to con a calling connection, su

means for controlling the selector over two sides of a line circuit in. series, said selector having means controlled by a called Aarty for reversingthe current in the said) line circuit, and a supervisory signal mechanism responsive to the said reversal 'of current.

5. In a telephone system, a plurality of subscribers lines, automatic trunkin switches one for each of said lines, a set o trunks, a combined automatic trunk selector and impulse repeater common to said lines provided'with means for automatically` grounding the so-called vertical side of any al the called party, and means for controlling said selector and repeater over two sides of a line circuit in series.

6. In a telephone system, a set of trunksl a combined automatictrlmk selector and impulse repeater, and a suitable subscrihers talking circuit over which said selector and repeater is controlled over the two. sides of fsaid circuit in series, said-selector and repeater having means controlled by a called party for reversing thev current in said line,

said selector-'repeater 'operating-to first seswitch for each trunk, an automatic trunk selector provided with'means for grounding any selected trunk to control the switch at the other end thereof by alternating onev or more ground impulses over one side of the -lect a trunk and to then repeat limpulses trunk with a single impulse over the other side thereof, means for directly controlling -saidselector over two sides of a line circuit said trunk selector having motion in one p ane -to'select rou s and motion in a plane at right ang es t ereto to ind a trunk in a selected group, a plurality of lines, and automatic trimking' switches therefor having access-in common to said trunk selector.

in series 10. In a telephone system, a plurality of A trunks divided into groups, an automatic switch for each trunk, an automatic trunk selector provided with means for grounding anyselected trunk to control'the switch at the other end thereof by alternating one or more ground impulses over one side of the trunk with a single impulse over the other side thereof, and means for controlling said selector over two sides of a line circuit in series, the said selector provided with mechanism for automatically causing an intermittent grounding of one side of the selected trunk, and means responsive to said side thereof, and means for controlling said selector over two sides of a line circuit iny series, said selector having means controlled by a called party for reversing the current in the said line circuit, said trunk selector having motion in one plane to select groups and motion in aeplane at right-angles thereto to lind a trunk in a selected group.

12. In a telephone system, a plurality of trunks divided int-o groups, an automatic switch for each trunk, an automatic trunk selector provided with means for grounding any selected trunk to control the switch at the other end thereof by alternating one or more ground impulses over one side of the trunk with a single impulse over the other side thereof, and means for controlling the selector over two sides of a line circuit in series, said selector `having means controlled by a called party for reversing the current in the said line circuit, and a supervisory signal mechanism responsive to the said reversal of current, said trunk selector having motion in one plane-to select groups and motion in a plane at right-angles thereto to ind atrunk in a selected group.

13. In av telephone system, a plurality of subscribers lines, automatic trunking switches one for each of said lines, a set of trunks divided into groups, a combined automatic trunk selector and impulse re-l peater common to said lines provided with means for automatically grounding the socalled vertical side of any selected trunk to signal the called party, and means for directly controlling said selector and repeater over two sides ofa line circuit in series, said trunk selector having one motion to select groups and a second motion to ind a trunk in a selected group'.

14. In a telephone system, a set of trunks divided into grou s, a combined automatic trunk selector an impulse repeater, and a suitable line over which said selector and repeater is controlled, said selector and rei,ae1,eee i peater having means controlled by a called party for reversing the current in said line,

lsaid trunk selector having motion in one motion in a plane at right-angles thereto to find a trunk in a selected group.

16. In a telephone system, a plurality of subscribers lines, automatic trunking switches one for each of said lines, a plurality of trunks, an automatic switch for each trunk, an automatic trunk selector common to said lines provided with means for grounding any selected trunk to control the switchrat the other end thereof by alternating one or more ground impulses over one side of the trunk with a single impulse over the other side thereof, means for directly controlling said selector over two sides of a line circuit in series, and one or more central .sources of operating and talking current.

17. In a telephone system, a plurality of trunks, an automatic switch for each trunk, an automatic trunk selector provided with means for grounding any selected trunk to control the switch at' the other4 end thereof by alternating one or more ground impulses over one side of the trunkwith a single impulse over the other side thereof, means for controlling said selector over two sides of a line circuit in series, the said selector provided With mechanism for automatically causing an intermittent grounding of one side of the selected trunk, means responsive to said intermittent grounding for transmitting a signal, and one or more central sources of operating and talking current.

18. In a telephone system, a plurality of trunks, an automatic switch for each trunk, an automatic trunk selector provided with means for grounding any selected trunk to control the switch at the other end thereof by alternating one or more ground impulses over one side of the trunk with a single impulse over the other side thereof, means for controlling said selector over two sides of a line circuit in series, said selector having means controlled by a called party for reversing the current in the said line circuit,

and one or more central sources of operating f and talking current.

19. In a telephone system, a plurality of trunks, an automatic switch for each trunk, an automatic trunk selector provided with means for grounding any selected trunk to control the switch at the other end thereof by alternating one or more ground impulses over one side of the trunk with a single impulse overthe other side thereof, means for controlling the selector over two-sides of a line circuit in series, said selector having means controlled by a called party for reversing the current 1n the said line circuit, a supervisory signal mechanism responsive to the said reversal of current, and one or more central sources of operating and talking current.

20. In a telephone system, a plurality of subscribers lines, automatic trunking switches one for each of said lines, a set of trunks, a combined automatic trunk selector and impulse repeater common to said lines provided with means for automatically grounding the so-called vertical side of any selected trunk to signal the called party, means for controlling said selector and repeater over two sides of a line circuit in series, and one or more central sources of operating and talking current.

21. In a telephone system, a set of trunks, a combined automatic trunk selector and impulse repeater, a suitable subscribers talking circuit over which said selector and repeater' is controlled over the two sides of said cir-- cuit in series, said selector and repeater having means controlled by a called party for reversing the current in said line, and one or more central sources of operating and talking current, said selector-repeater operating to first select a trunk and to then repeat impulses over said trunk.

22. In a telephone system, a cord circuit provided with supervisory signal mechanism, a rela controlled by the called party for reversing the current in said cord circuit to control said mechanism, and one or more central sources of operating and talking current.

23. In a telephone system, means including a cord circuit and one or more automatic switches for semi-automatically extending a calling connection, supervisory signal mechanism for said cord circuit, means controlled by the called rent in said cord circuit to control said mechanism, and one or'more central sources of operating and talking current.

24. In a telephone system, a plurality of trunks, an automatic switch for each trunk, an automatic trunk selector provided with means for grounding any selected trunk to control the switch at the other end thereof by alternating one or more ground impulses over one side of pulse over the other side thereof, and means for controlling said selector over two sides of a line circuit in series, the said selector provided with mechanism for automatically causing an intermittent grounding of one party for reversing the cur- A the trunk with a single im-v side of the selected trunk, and means responsive to said intermittent ounding for controlling the application o? ringing current onto the called line.

25. In a telephone system, a plurality of trunks, an automatic switch for each trunk, an automatic trunk selector provided with means for grounding any selected trunk to control the switch at the other end thereof by alternating one or more ground impulses over one side of the trunk with a single impulse over the other side thereof, and means for controlling said selector over two sides of a line circuit in series, the said selector provided with a step-by-step switch, contacts controlled by said switch, means for closing said contacts after said switch has been moved a predetermined number of steps, and means controlled by the closing of said contacts for controlling the application of ringing current to the called line.

26. In a telephone system, a plurality of trunks, an automatic switch for each trunk, an automatic trunk selector provided with means for grounding any selected trunk to control the switch at the other end thereo by alternating one or more ground impulses over one side of the trunk with a single impulse over the other side thereof, and means for controlling said selector over two sides of a line circuit in series, the said selector provided with a step-by-step switch, means for operating said switch one step in response to each series of impulses representing the various digits of the called number, a pair of contacts controlled by said switch, means for closingI said contacts after said switch has been moved a predetermined number 'of steps, and means controlled by the closing of said contacts for controlling the application of ringing current to the called line.

27. In a telephone system, a plurality oi trunks, an automatic switch for each trunk, an automatic trunk selector provided with means for grounding any selected trunk to control the switch at the other end thereof by alternating one or more ground impulses over one side of the trunk with a single impulse over the other side thereof, and means l`for controlling said selector over two sides of a line circuit in series, the said selector provided with a step-by-step switch, contacts controlled by said switch, means for closing said contacts after said switch has been moved a predetermined number of steps, means controlled by the closing of sald contacts for automatically causing an intermittent grounding of one side of the selected trunk, and means responsive to sald intermittent grounding for controlling the application of ringing current to the called line.

. 28. In a telephone system, a plurality oftrunks, an automatic switch for each trunk,

an automatic trunk selector' provided with net means for grounding any selected trunk to control the switch at the other end thereof by alternating one or more ground impulses over one side of the trunk with a single impulse over the other side thereof, and means for controlling said selector over two sides of a line circuit in series, the said selector provided with a step-by-step switch, means for operating said switch one step in response to each series of impulses yrepresenting the various digits of the called number, a pair of contacts controlled by said switch, means for closing said contacts after said switch has been vmoved a predetermined lnumber. of steps, means controlled by the closing of said contacts for automatically causing an intermittent grounding of one side of the selected trunk, and means responsive to said intermittent grounding for controlling the application of ringing current to the called line.

29. In a telephone system, a plurality of subscribers lines, means for establishing aconnection between two of said lines, said means including a cord circuit and one or more automatic switches, a pair of line relays bridged across one of said automatic switches, a supervisory signal in said cord ,c1rcu1t,means controlled by the response of by said polarized relay, a pair of line relays bridged across one of said automatic erate said supervisory signal.

31. In a telephone system, a plurality of subscribers lines, means for extending a connection between two of said lines, said means including a cord circuit and one or more automatic switches, a pair of line relays bridged across the line at one of said automatic switches, a supervisory relay in said cord circuit, means operated upon the response of the called subscriber for transmitting talking current back from the called line, means controlled by said talking cur rent for energizing said line relays, means controlled bythe energization of said line relays for reversing the current through said supervisory relay, and a supervisory signal controlled by Said supervisory relay.

32. In a telephone system, a non-numerical trunking switch controlled over two sides of a talking circuit in series for trunking a connection to an operator, a repeater. controlled over two sides of the talking circuit in series for repeating impulses to one side of a section of the talkin v circuit, and a cord circuit for connectingsaid extended connection to the manual boardwith the repeater.

Signed by me at Chicago, Cook county, lllinois, this 1st day of December, 191Q. l

TALBOT Gr. MARTlN.

Witnesses:

ARTHUR J. RAY, E. D. FALES. 

